The present invention relates to an ion implantation system and an ion implantation method and, more particularly, to an ion implantation system and an ion implantation method suitable for introducing various ions including oxygen ions into silicon wafers.
Recently, an ion implantation system for separation by implanted oxygen (hereinafter abbreviated to xe2x80x9cSiMOXxe2x80x9d) has been developed. The ion implantation system for SiMOX introduces oxygen ions in a surface region of a predetermined depth of a silicon wafer, and subjects the silicon wafer to an annealing process to form a SiO2 layer in the silicon wafer. When the SiO2 layer is used as an insulating substrate, the wafer capable of quick response, as compared with that of a conventional wafer having a silicon layer formed on a SiO2 substrate, can be realized.
The ion implantation system for SiMOX carries out a high-temperature process in which an ion beam is applied to a wafer uniformly heated at 100xc2x0 C. or above. The temperature of the wafer is an important factor, and various wafer heating systems and various heating structures have been used.
Generally, when irradiating a plurality of wafers held by a wafer holder, i.e., a wafer holding means, with an ion beam, the wafer holder is rotated and the wafers turning together with the wafer holder are irradiated with the ion beam intermittently to reduce thermal stress that may be induced in the wafers by the ion beam. If the intensity distribution of the ion beam is less than a necessary accuracy of implantation uniformity, the ion beam must be converged to some extent and the ion beam must be projected so as to move relative to the wafers for scanning.
A scanning system in which the wafers are kept stationary and the beam is moved for scanning is called a beam scanning system. A scanning system in which the ion beam is kept stationary and the wafers are moved for scanning is called a mechanical scanning system. Since the latter system rotates a wafer holder holding wafers to move the wafers relative to an ion beam for scanning, it is difficult to determine the position of a heating mechanism for heating the wafers. Generally, the heating mechanism is disposed fixedly on a scanning path relative to the wafer holder and heats the wafers as the wafers pass by the heating mechanism.
This conventional system is unable to heat the wafers sufficiently in regions other than a region in the vicinity of the heating mechanism. Therefore, the wafers cannot be uniformly heated at a high temperature, ions are implanted at a low efficiency and the efficiency of the system is low. This may be prevented by using a large heating mechanism having a high heating ability and heating for a long time, which, however, enlarges the system and reduces efficiency greatly.
The present invention has been made in view of the foregoing problems and it is therefore an object of the present invention to provide an ion implanting system and an ion implantation method capable of uniformly heating wafers at a high temperature at all times regardless of the scanning motion of a wafer holding means.
To achieve the object, the present invention provides an ion implanting system comprising a heating means for heating wafers held by a wafer holding means, and a relative position changing means for changing the position of the wafer holding means relative to an ion beam in a plane substantially perpendicular to the ion beam, wherein the heating means and the relative position changing means move synchronously.
When the wafer holding means includes a rotary disk capable of holding a plurality of wafers on its peripheral part and the relative position changing means includes a rotating means for rotating the rotary disk in a plane substantially perpendicular to the ion beam and a swinging means for swinging the rotary disk in a plane substantially perpendicular to the ion beam, the heating means is combined with the swinging means, and the swinging means and the heating means move synchronously.
When the rotating means for rotating the rotary disk has a driving mechanism installed in a swing box to rotate the rotary disk about an axis of rotation, and the swinging means for swinging the rotary disk reciprocates the rotary disk laterally about a swinging axis relative to the ion beam to move the rotary disk for scanning, the heating means is combined with the swinging means, and the heating means moves in synchronism with the scanning movement of the rotary disk.
To achieve the object, the present invention provides an ion implantation method that introduces ions having a predetermined mass and separated from an ion beam projected by an ion source into a heated wafer while moving in synchronism with a relative position changing means that changes the position of the ion beam.
The ion implantation method is characterized in rotating a rotary disk holding a plurality of wafers on its peripheral part and swinging the rotary disk in a plane perpendicular to the ion beam by a swinging means when introducing the ions having the predetermined mass and separated from the ion beam projected by an ion source into the wafers.
The ion implantation method is characterized in rotating a rotary disk holding a plurality of wafers on its peripheral part to turn the wafers by a driving mechanism disposed in a swing box when introducing ions having a predetermined mass and separated from an ion beam projected by an ion source into the wafers, and laterally reciprocating the swing box relative to the ion beam to apply the ion beam to the heated wafers while the rotary disk moves in synchronism with a scanning operation of the swing box.
The heating means remains at an optimum heating position and is able to perform the same scanning operation as the wafer holding means even if the wafer holding means (rotary disk) holding the wafers performs a scanning operation. Therefore, the wafers can be most properly heated at all times regardless of the scanning position of the wafer holding means to achieve the foregoing object.